Korean Patent No. 10-910348 (Patent Document 1), for example, discloses a tablet including a resonance circuit and sensing a location of an electronic pen emitting an electromagnetic wave of a certain frequency.
FIG. 1 illustrates a summary of technology disclosed in Patent Document 1. Referring to FIG. 1, a tablet may include a loop antenna 10 forming a closed loop, a plurality of line antennas 20, each having one end electrically connected to the loop antenna 10, having a comb shape and parallelly arranged across the loop antenna 10, a multiplexer 30, in which the other ends of the line antennas 20 that are not connected to the loop antenna 10 are connected to a plurality of input sides and any one of the input sides is selected as an output side, and a differential amplifier 40 having one input connected to the loop antenna 10 and the other one input is connected to the output side of the multiplexer 30, to thus output a difference between an electric potential of the loop antenna 10 and an electric potential of the line antenna 20 selected by the multiplexer 30.
In the above structure, when an electric pen emitting an electromagnetic wave approaches a certain location inside a closed loop of the loop antenna 10, that is, in a virtually set electric pen sensing area, an induction voltage is generated by an electromagnetic induction effect in all line antennas 20. In this state, the generated induction voltages show different amplitudes and phases in the respective line antennas with respect to an electric potential of the loop antenna 10. Patent Document 1 discloses a tablet for measuring a location of an electric pen by using the phenomenon.
Meanwhile, FIG. 2 illustrates a technology as a method of implementing a touch panel for sensing a touch of a human finger and a location of a touch. First, a plurality of line antennas arranged in the form of a lattice of an X-axis and a Y-axis is formed. In this state, an X-axis line antenna 21 and a Y-axis line antenna 22 may be insulated from each other or arranged on different surfaces of a substrate to prevent electric connection therebetween.
An X-axis analog switch 37 is arranged at one end of the X-axis line antennas 21 to be selectively connected to a TX circuit 51. The other end of the X-axis line antennas 21 is open. In addition, one end of the Y-axis line antennas 22 is connected to an RX circuit 52 via a Y-axis analog switch 38. The other side end of the Y-axis line antennas 22 is open.
In the above structure, the TX circuit 51 connects a drive signal having a certain voltage (or current) and a waveform to any one of the X-axis line antennas 21. In this state, the Y-axis analog switch 38 selects the Y-axis line antennas 22 one by one and measures a signal (a voltage or current by the drive signal) sensed through the RX circuit 52. Next, the drive signal is connected to another X-axis line antenna 21, and in this state, the Y-axis line antennas 22 are selected one by one. Then, a scan operation for sensing a signal of each selected one of the Y-axis line antennas 22 through the RX circuit 52 is performed. By using the signal sensed through the scan operation, the X-axis line antenna 21 and the Y-axis line antenna 22 passing a location where a finger contacts or approaches may be found out. Thus, a coordinate of a location where a finger contacts may be obtained by using the X-axis line antenna 21 and the Y-axis line antenna 22 found as above.
Meanwhile, the above tablet apparatus or touch panel may be arranged on a front surface of a display device. In this case, an antenna pattern formed in the sensing area may be designed to be as transparent as possible.
In addition, to keep with various user demands, an apparatus capable of simultaneously performing a precise manipulation input using an electric pen and a touch input by a finger with respect to a display device is demanded.
In addition, there is a demand for minimizing the width of an edge portion where circuit devices for driving an antenna pattern are arranged, as a portion surrounding the sensing area where the antenna pattern is arranged increases rapidly.